Embodiments of the present disclosure generally relate to an energy exchange assembly, and, more particularly, to an energy exchange assembly having one or more membranes that are configured to transfer sensible and/or latent energy therethrough.
Energy exchange assemblies are used to transfer energy, such as sensible and/or latent energy, between fluid streams. For example, air-to-air energy recovery cores are used in heating, ventilation, and air conditioning (HVAC) applications to transfer heat (sensible energy) and moisture (latent energy) between two airstreams. A typical energy recovery core is configured to precondition outdoor air to a desired condition through the use of air that is exhausted out of the building. For example, outside air is channeled through the assembly in proximity to exhaust air. Energy between the supply and exhaust air streams is transferred therebetween. In the winter, for example, cool and dry outside air is warmed and humidified through energy transfer with the warm and moist exhaust air. As such, the sensible and latent energy of the outside air is increased, while the sensible and latent energy of the exhaust air is decreased. The assembly typically reduces post-conditioning of the supply air before it enters the building, thereby reducing overall energy use of the system.
Energy exchange assemblies such as air-to-air recovery cores may include one or more membranes through which heat and moisture are transferred between air streams. Each membrane may be separated from adjacent membranes using a spacer. Stacked membrane layers separated by spacers form channels that allow air streams to pass through the assembly. For example, outdoor air that is to be conditioned may enter one side of the device, while air used to condition the outdoor air (such as exhaust air or scavenger air) enters another side of the device. Heat and moisture are transferred between the two airstreams through the membrane layers. As such, conditioned supply air may be supplied to an enclosed structure, while exhaust air may be discharged to an outside environment, or returned elsewhere in the building.
In an energy recovery core, for example, the amount of heat transferred is generally determined by a temperature difference and convective heat transfer coefficient of the two air streams, as well as the material properties of the membrane. The amount of moisture transferred in the core is generally governed by a humidity difference and convective mass transfer coefficients of the two air streams, but also depends on the material properties of the membrane.
Many known energy recovery assemblies that include membranes are assembled by either wrapping the membrane or by gluing the membrane to a substrate. Notably, the design and assembly of an energy recovery assembly may affect the heat and moisture transfer between air streams, which impacts the performance and cost of the device. For example, if the membrane does not properly adhere to the spacer, an increase in air leakage and pressure drop may occur, thereby decreasing the performance (measured as latent effectiveness) of the energy recovery core. Conversely, if excessive adhesive is used to secure the membrane to the spacer, the area available for heat and moisture transfer may be reduced, thereby limiting or otherwise reducing the performance of the energy recovery core. Moreover, the use of adhesives in relation to the membrane also adds additional cost and labor during assembly of the core. Further, the use of adhesives may result in harmful volatile organic compounds (VOCs) being emitted during initial use of an energy recovery assembly.
While energy recovery assemblies formed through wrapping techniques may reduce cost and minimize membrane waste, the processes of manufacturing such assemblies are typically labor intensive and/or use specialized automated equipment. The wrapping may also result in leaks at edges due to faulty seals. For example, gaps typically exist between membrane layers at corners of an energy recovery assembly. Further, at least some known wrapping techniques result in a seam being formed that extends along membrane layers. Typically, the seam is sealed using tape, which blocks pore structures of the membranes, and reduces the amount of moisture transfer in the assembly.